/* readobj.c - read object file for linker */

/* Copyright (C) 1994 Bruce Evans */

#include "syshead.h"
#include "ar.h"			/* maybe local copy of <ar.h> for cross-link */
#include "const.h"
#include "byteord.h"
#include "obj.h"
#include "type.h"
#include "globvar.h"

/*
   Linking takes 2 passes. The 1st pass reads through all files specified
in the command line, and all libraries. All public symbols are extracted
and stored in a chained hash table. For each module, its file and header
data recorded, and the resulting structures are chained together
(interleaved with the symbols).

   The symbol descriptors are separated from the symbol names, so we must
record all the descriptors of a module before putting the symbols in the
symbol table (poor design). The descriptors are stored in the symbol
table, then moved to the top of the table to make room for the symols.
The symbols referred to in a given module are linked together by a chain
beginning in the module descriptor.
*/

static unsigned convertsize[NSEG / 4] = {0, 1, 2, 4};
static struct entrylist *entrylast;	/* last on list of entry symbols */
static struct redlist *redlast;	/* last on list of redefined symbols */
static struct modstruct *modlast;	/* data for last module */

static long readarheader(char **parchentry);
static unsigned readfileheader(void);
static void readmodule(char *filename, char *archentry);
static void reedmodheader(void);
static bool_pt redsym(struct symstruct *symptr, bin_off_t value);
static unsigned checksum(char *string, unsigned length);
static unsigned segbits(unsigned seg, char *sizedesc);

/* initialise object file handler */

void objinit(void)
{
    modfirst = modlast = NUL_PTR;
    entryfirst = entrylast = NUL_PTR;
    redfirst = redlast = NUL_PTR;
}

/* read all symbol definitions in an object file */

void readsyms(char *filename, bool_pt trace)
{
    char *archentry;
    long filelength;
    char filemagic[SARMAG];
    unsigned long filepos;
    unsigned modcount;

    if (trace)
	errtrace(filename, 0);
    openin(filename);		/* input is not open, so position is start */
    switch ((unsigned) readsize(2))
    {
    case OMAGIC:
	seekin((unsigned long) 0);
	for (modcount = readfileheader(); modcount-- != 0;)
	    readmodule(filename, (char *) NUL_PTR);
	break;
    default:
	seekin((unsigned long) 0);
	readin(filemagic, sizeof filemagic);
	if (strncmp(filemagic, ARMAG, sizeof filemagic) != 0)
	    input1error(" has bad magic number");
	filepos = SARMAG;
	while ((filelength = readarheader(&archentry)) > 0)
	{
	    unsigned int magic;
	    if (trace)
		errtrace(archentry, 2);
	    filepos += sizeof(struct ar_hdr);
            magic = (unsigned) readsize(2);
            if(magic == OMAGIC)
	    {
	        seekin(filepos);
	        for (modcount = readfileheader(); modcount-- != 0;)
	        {
		    readmodule(stralloc(filename), archentry);
		    modlast->textoffset += filepos;
	        }
	    }
	    else if( magic == 0x3C21 ) /* "!<" */
	       filelength = SARMAG;
	    seekin(filepos += ld_roundup(filelength, 2, long));
	}
	break;
    }
    closein();
}

/* read archive header and return length */

static long readarheader(char **parchentry)
{
    struct ar_hdr arheader;
    char *endptr;
    char *nameptr;

    if (readineofok((char *) &arheader, sizeof arheader))
	return 0;
    strncpy (*parchentry = nameptr = ourmalloc(sizeof arheader.ar_name + 1),
	     arheader.ar_name, sizeof arheader.ar_name);
    endptr = nameptr + sizeof arheader.ar_name;
    do
	*endptr-- = 0;
    while (endptr > nameptr && (*endptr == ' ' || *endptr == '/'));
    return strtoul(arheader.ar_size, (char **) NUL_PTR, 0);
}

/* read and check file header of the object file just opened */

static unsigned readfileheader(void)
{
    char fileheader[5];

    readin(fileheader, sizeof fileheader);
    if ((unsigned char)fileheader[4] != checksum(fileheader, 4))
	input1error(" is not an object file (checksum failed)");
    return c2u2(fileheader + 2);
}

/* read the next module */

static void readmodule(char *filename, char *archentry)
{
    struct symdstruct		/* to save parts of symbol before name known */
    {
	bin_off_t dvalue;
	flags_t dflags;
    };
    struct symdstruct *endsymdptr;
    flags_t flags;
    unsigned nsymbol;
    struct symdstruct *symdptr;
    char *symname;
    struct symstruct **symparray;
    struct symstruct *symptr;

    reedmodheader();
    modlast->filename = filename;
    modlast->archentry = archentry;
    nsymbol = readsize(2);
    symdptr = (struct symdstruct *)
	ourmalloc(nsymbol * sizeof(struct symdstruct));
    for (endsymdptr = symdptr + nsymbol; symdptr < endsymdptr; ++symdptr)
    {
	readsize(2);		/* discard string offset, assume strings seq */
	symdptr->dflags = flags = readsize(2);
	symdptr->dvalue = readconvsize((flags & SZ_MASK) >> SZ_SHIFT);
	/* NB unsigned flags to give logical shift */
	/* bug in Xenix 2.5 cc causes (int) of the */
	/* argument to turn flags into an int */
    }
    symdptr = (struct symdstruct *)
	moveup(nsymbol * sizeof(struct symdstruct));
    modlast->symparray = symparray = (struct symstruct **)
	ourmalloc((nsymbol + 1) * sizeof(struct symstruct *));
    symname = readstring();	/* module name */
    modlast->modname = stralloc(symname);	/* likely OK overlapped copy */
    for (endsymdptr = symdptr + nsymbol; symdptr < endsymdptr;
	 *symparray++ = symptr, release((char *) ++symdptr))
    {
	symname = readstring();
	if ((flags = symdptr->dflags) & (E_MASK | I_MASK) &&
	    (symptr = findsym(symname)) != NUL_PTR)
	{
	    /*
	       weaken segment-checking by letting the maximum segment
	       (SEGM_MASK) mean any segment
	    */
	    if ((symptr->flags & SEGM_MASK) == SEGM_MASK)
		symptr->flags &= ~(flags_t) SEGM_MASK | (flags & SEGM_MASK);
	    else if ((flags & SEGM_MASK) == SEGM_MASK)
		flags &= ~(flags_t) SEGM_MASK | (symptr->flags & SEGM_MASK);
	    if ((flags ^ symptr->flags) & (A_MASK | SEGM_MASK))
	    {
		redefined(symname, " with different segment or relocatability",
			  archentry, symptr->modptr->filename,
			  symptr->modptr->archentry);
		continue;
	    }
	    if (symptr->flags & E_MASK)
	    {
		if (flags & E_MASK && redsym(symptr, symdptr->dvalue))
		    redefined(symname, "", archentry, symptr->modptr->filename,
			      symptr->modptr->archentry);
		continue;
	    }
	    if (flags & I_MASK && symdptr->dvalue <= symptr->value)
		continue;
	}
	else
	    symptr = addsym(symname);
	symptr->modptr = modlast;
	symptr->value = symdptr->dvalue;
	symptr->flags = flags;
	if (flags & N_MASK)
	    entrysym(symptr);
    }
    *symparray = NUL_PTR;
}

/* put symbol on entry symbol list if it is not already */

void entrysym(struct symstruct *symptr)
{
    register struct entrylist *elptr;

    for (elptr = entryfirst; elptr != NUL_PTR; elptr = elptr->elnext)
	if (symptr == elptr->elsymptr)
	    return;
    elptr = (struct entrylist *) ourmalloc(sizeof(struct entrylist));
    elptr->elnext = NUL_PTR;
    elptr->elsymptr = symptr;
    if (entryfirst == NUL_PTR)
	entryfirst = elptr;
    else
	entrylast->elnext = elptr;
    entrylast = elptr;
}

/* read the header of the next module */

static void reedmodheader(void)
{
    struct
    {
	char htextoffset[4];	/* offset to module text in file */
	char htextsize[4];	/* size of text (may be 0 for last mod) */
	char stringssize[2];	/* size of string area */
	char hclass;		/* module class */
	char revision;		/* module revision */
    }
     modheader;
    unsigned seg;
    unsigned count;
    char *cptr;
    struct modstruct *modptr;

    readin((char *) &modheader, sizeof modheader);
    modptr = (struct modstruct *) ourmalloc(sizeof(struct modstruct));
    modptr->modnext = NUL_PTR;
    modptr->textoffset = c4u4(modheader.htextoffset);
    modptr->class = modheader.hclass;
    readin(modptr->segmaxsize, sizeof modptr->segmaxsize);
    readin(modptr->segsizedesc, sizeof modptr->segsizedesc);
    cptr = modptr->segsize;
    for (seg = 0; seg < NSEG; ++seg)
    {
	if ((count = segsizecount(seg, modptr)) != 0)
	{
	    if (cptr == modptr->segsize)
		ourmalloc(count - 1);	/* 1st byte reserved in struct */
	    else
		ourmalloc(count);
	    readin(cptr, count);
	    cptr += count;
	}
    }
    if (modfirst == NUL_PTR)
	modfirst = modptr;
    else
	modlast->modnext = modptr;
    modlast = modptr;
}

static bool_pt redsym(struct symstruct *symptr, bin_off_t value)
{
    register struct redlist *rlptr;
    char class;

    if (symptr->modptr->class != (class = modlast->class))
	for (rlptr = redfirst;; rlptr = rlptr->rlnext)
	{
	    if (rlptr == NUL_PTR)
	    {
		rlptr = (struct redlist *)
		    ourmalloc(sizeof(struct redlist));
		rlptr->rlnext = NUL_PTR;
		rlptr->rlsymptr = symptr;
		if (symptr->modptr->class < class)
		    /* prefer lower class - put other on redlist */
		{
		    rlptr->rlmodptr = modlast;
		    rlptr->rlvalue = value;
		}
		else
		{
		    rlptr->rlmodptr = symptr->modptr;
		    symptr->modptr = modlast;
		    rlptr->rlvalue = symptr->value;
		    symptr->value = value;
		}
		if (redfirst == NUL_PTR)
		    redfirst = rlptr;
		else
		    redlast->rlnext = rlptr;
		redlast = rlptr;
		return FALSE;
	    }
	    if (symptr == rlptr->rlsymptr && class == rlptr->rlmodptr->class)
		break;
	}
    return TRUE;
}

static unsigned checksum(char *stringp, unsigned length)
{
    unsigned char sum;		/* this is a 1-byte checksum */
    unsigned char *string = (unsigned char *)stringp;

    for (sum = 0; length-- != 0;)
	sum += *string++ & 0xFF;
    return sum;
}

bin_off_t readconvsize(unsigned countindex)
{
    return readsize(convertsize[countindex]);
}

bin_off_t readsize(unsigned count)
{
    char buf[MAX_OFFSET_SIZE];

    if (count == 0)
	return 0;
    readin(buf, count);
    return cntooffset(buf, count);
}

static unsigned segbits(unsigned seg, char *sizedesc)
{
    return 3 & ((unsigned) sizedesc[((NSEG - 1) - seg) / 4] >> (2 * (seg % 4)));
    /* unsigned to give logical shift */
}

unsigned segsizecount(unsigned seg, struct modstruct *modptr)
{
    return convertsize[segbits(seg, modptr->segsizedesc)];
}
